Says it would zoom past Barnard's Star in 50 years at 12.5% the speed of light because it is not designed to go into orbit. So, it is just getting a quick look there and everyplace else it travels. By the time this thing could be built, sensor technology might be up to the task.

So then what do you do when you pass the heilopause and you no longer have a solar "wind"?

Honestly a redesign using ion engines of today would make a different craft. Plus it would allow the craft to not just speed on by in a ballistic trajectory, but even start breaking and enter a orbit that would allow the craft to stay and radio back info.

It can be electrically powered by Nuclear reactors, and as each one get's past it's 20 year lifespan you jettison it making the craft lighter. Ion engines already are producing impressive thrust for the age of the technology. An unmanned interstellar probe moving at 12% the speed of light, assuming it does not plow into something out there is a very feasible project and could gather scientific data the entire way. Although the Doppler effect on communications would be interesting. But research into really measuring time dilation could be done as well.

Sadly, we are far more interested in killing each other. It's more important to fund the war machine than the thinking machine.

Antimatter reactions are ridiculously energetic, with an energy density of some 90PJ/kg. The problem is that there is no known naturally occurring source of antimatter, we have to produce all that we want to use. That makes it nothing more than a battery technology. Add in the inefficiencies of antimatter production, and you're talking about energy requirements equivalent to centuries at our current global consumption rate just to get into orbit. Finding a way to densely store the stuff is just one of many very difficult problems that need to be solved.

Oddly enough, I was reading up on possible interstellar probes just a few days ago.

Anyway, getting to another star system is just simply such a huge task. Take for example Daedalus' design -- the economics of building such a vehicle today are such that even if we had the political willpower to do so, it would just cost so much that it would soak up our global economic output for a very long time, possibly centuries.

If we were to just wait 100 years or so, I'd put money on new physics being discovered which would allow an interstellar mission to be constructed for a tiny fraction of the cost of Daedalus (or Icarus), be completed in a fraction of the time, and have enormously increased capabilities (e.g. stopping at the target star, making a return journey, or even carrying Astronauts).

It's an interesting study, but totally impractical today. We need a better understanding of the universe before we should even give serious thought to attempting this -- it doesn't pass the back-of-the-envelope test.

It's not completely absurd. The projects that mankind undertakes today are enormous (in fact, there are multiple things that are way more expensive or complicated than this Daedalus spaceship). Take for example the entire road system of the world, including all rural roads, cities, traffic lights, cars, trucks, and whatnot. It's been an enormous undertaking - yet we don't mind rebuilding it entirely every decade because we don't like bumpy old asphalt or old cars.

The ISS, with a weight of nearly 400 tons, and measuring 50x100 meters shows how much is possible for a relatively small-scale human project. All our civil achievements show how much is possible for the large-scale human projects. We don't mind changing the entire surface of our planet.

We humans look at cost/benefit estimates. If the costs are high, we don't mind, as long as the benefits are there.

The problem therefore with the Daedalus is not that it's not possible. It is that it just does not have enough benefits for mankind to invest the time, effort and resources in it.

In singular perhaps, but not in aggregate. US DoD funding for one year dwarfs the ISS. I personally would rather invest in something that can pay dividends even if the payout is some distance off. The slaughter of man and the destruction of infrastructure doesn't fit that bill. Stop making swords, start making pens, and go put the savings to productive use.